Moving work-in-process materials inside a manufacturing area has commonly been with wheeled vehicles, conveyance devices (such as overhead cranes controlled in real time by a human operator) and powered or gravity-feed conveying systems (utilizing belts, rollers, etc.). With wheeled vehicles, much floor space has to be given up to open areas in order to permit the vehicles room in which to maneuver. There have also been several control problems inherent to wheeled vehicles, creating traffic jams and lapses in proper computer control, all of which results in severe inefficiencies. In the case of overhead crane systems, few of them can run without the crane operator's constant attention; indeed, a second person must usually act to hook the crane to the load, guide the crane operator's actions with hand signals and, finally, unhook the load at its destination. Gravity and belt- or roller-powered conveyors also require much floor space for their installation. In addition, the finished conveyor system is usually quite product-specific, exhibiting little tolerance for new products to be integrated onto the manufacturing floor.
For transporting items substantially horizontally, conveyor belts and other mechanisms typically require, for support, structure on both ends of the conveying means. Unfortunately, the support scheme often requires additional floor space and/or complexity of apparatus. Moreover, due to the nature of such supported conveying means, the overall length is generally fixed. The foregoing constraints limit the flexibility of such conveying systems.
While the use of chains provides flexibility, there has been a long sought need to develop a chain that need not be supported on both ends. A flexible chain and rigid bar combination was disclosed in U.S. Pat. No. 4,885,907 (issued to Sofia Pappanikolaou). This so-called chainbar requires separate locking mechanisms and a plurality of moving parts, which are susceptible to failure under load.
U.S. Pat. No. 1,004,575 (issued to J. M. Jones) also addresses the support problem by providing hook prominences. Unfortunately, such prominences tend to catch on fabric and other extraneous objects. Moreover, no provision is made to accommodate the drive sprocket teeth which are normally expected to drive the chain when in use by engaging slots in the chain placed in line at regular intervals.
U.S. Pat. No. 553,650 (issued to P. S. Kingsland) discloses a lock chain which is rigid only when first laid straight and then compressed end-to-end. Such a procedure is not conducive to modern material handling operations.
It would be advantageous to eliminate the use of wheeled vehicles for moving work-in-process, saving floor space in a manufacturing area.
It would also be advantageous to replace the overhead crane operators with full-time computer control, removing the potential for human error and reducing the number of people needed to operate in a given manufacturing floor area.
It would be further advantageous to reduce the transportation time of parts, minimizing the amount of work- in-process inventory needed in a manufacturing area.
It would be yet advantageous to keep all movement of work-in-process (WIP) off the floor level and place it overhead. This would minimize the danger of accident by eliminating the mixing of WIP transportation with human activities at floor level, effectively eliminating floor conveyor systems in manufacturing plants which make individual pieces of a product. This thereby saves much floor space and provides a system that can be much more receptive to the introduction of new products on the manufacturing floor.